Method of providing an interface to a plurality of peripheral devices using bus adapter chips

ABSTRACT

A method of electrically coupling a central processing unit (CPU) of a network server to a plurality of network interface modules. The method comprises providing each of the plurality of network interface modules with a respective bus adapter chip to route an I/O bus having a first format from the central processing unit to a primary side of each of the plurality of bus adapter chips and routing another I/O bus of the first format from a secondary side of each of the plurality of bus adapter chips to respective ones of the network interface modules. The bus adapter chips also provide for arbitered access along the I/O buses and isolation of the CPU from electrical disruption when one of the network interface modules is removed.

RELATED APPLICATIONS

This application is a continuation of and claims priority under 35U.S.C. § 120 to co-pending U.S. patent application Ser. No. 08/943,044,filed on Oct. 1, 1997, and entitled “METHOD FOR HOT SWAPPING OF NETWORKCOMPONENTS.”

Moreover, the benefit under 35 U.S.C. § 119(e) of the following U.S.provisional application(s) is hereby claimed:

Application Title No. Filing Date “Hardware and Software Architecturefor 60/047,016 May 13, 1997 Inter-Connecting an Environmental ManagementSystem with a Remote Interface” “Self Management Protocol for a60/046,416 May 13, 1997 Fly-By-Wire Service Processor” “IsolatedInterrupt Structure for 60/047,003 May 13, 1997 Input/OutputArchitecture” “Three Bus Server Architecture with 60/046,490 May 13,1997 a Legacy PCI Bus and Mirrored I/O PCI Buses” “Computer SystemHardware 60/046,398 May 13, 1997 Infrastructure for Hot Plugging Singleand Multi-Function PC Cards Without Embedded Bridges” “Computer SystemHardware 60/046,312 May 13, 1997 Infrastructure for Hot PluggingMulti-Function PCI Cards With Embedded Bridges”

The subject matter of U.S. Pat. No. 6,175,490 entitled “FAULT TOLERANTCOMPUTER SYSTEM”, issued on Jan. 16, 2001, is related to thisapplication.

APPENDICES

Appendix A, which forms a part of this disclosure, is a list of commonlyowned co-pending U.S. patent applications. Each one of the applicationslisted in Appendix A is hereby incorporated herein in its entirety byreference thereto.

COPYRIGHT RIGHTS

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent files or records, but otherwise reserves all copyrightrights whatsoever.

BACKGROUND OF THE INVENTION

Network servers and the accompanying local area networks (LANs) haveexpanded the power and increased the productivity of the work force. Itwas just a few years ago that every work station had a standalonepersonal computer incapable of communicating with any other computers inthe office. Data had to be carried from person to person by diskette.Applications had to be purchased for each standalone personal computerat great expense. Capital intensive hardware such as printers wereduplicated for each standalone personal computer. Security and backingup the data were immensely difficult without centralization.

Network servers and their LANs addressed many of these issues. Networkservers allow for resource sharing such as sharing equipment,applications, data, and the means for handling data. Centralized backupand security were seen as definite advantages. Furthermore, networksoffered new services such as electronic mail. However, it soon becameclear that the network servers could have their disadvantages as well.

Centralization, hailed as a solution, developed its own problems. Apredicament that might shut down a single standalone personal computerwould, in a centralized network, shut down all the networked workstations. Small difficulties easily get magnified with centralization,as is the case with the failure of a network server interface card(NIC), a common dilemma. A NIC may be a card configured for Ethernet,LAN, or Token-Ring to name but a few. These cards fail occasionallyrequiring examination, repair, or even replacement. Unfortunately, theentire network has to be powered down in order to remove, replace orexamine a NIC. Since it is not uncommon for modern network servers tohave sixteen or more NICs, the frequency of the problem compounds alongwith the consequences. When the network server is down, none of theworkstations in the office network system will be able to access thecentralized data and centralized applications. Moreover, even if onlythe data or only the application is centralized, a work station willsuffer decreased performance.

Frequent down times can be extremely expensive in many ways. When thenetwork server is down, worker productivity comes to a stand still.There is no sharing of data, applications or equipment such as spreadsheets, word processors, and printers. Bills cannot go out and orderscannot be entered. Sales and customer service representatives are unableto obtain product information or pull up invoices. Customers browsing orhoping to browse through a network server supported commercial web pageare abruptly cut off or are unable to access the web pages. Suchfrustrations may manifest themselves in the permanent loss of customers,or at the least, in the lowering of consumer opinion with regard to avendor, a vendor's product, or a vendor's service. Certainly, down timefor a vendor's network server will reflect badly upon the vendor'sreliability. Furthermore, the vendor will have to pay for more servicecalls. Rebooting a network server, after all, does require a certainamount of expertise. Overall, whenever the network server has to shutdown, it costs the owner both time and money, and each server shut downmay have ramifications far into the future. The magnitude of thisproblem is evidenced by the great cost that owners of network serversare willing to absorb in order to avoid down time through the purchaseof uninterruptible power supplies, surge protects, and redundant harddrives.

What is needed to address these problems is an apparatus that canlocalize and isolate the problem module from the rest of the networkserver and allow for the removal and replacement of the problem modulewithout powering down the network server.

SUMMARY OF THE INVENTION

The present invention includes methods of removing and replacing dataprocessing circuitry. In one embodiment, the method comprises changingan interface card in a computer comprising removing a network interfacemodule from the computer without powering down the computer and removingan interface card from the network interface module. The further acts ofreplacing the interface card into the network interface module andreplacing the network interface module into the computer withoutpowering down the network computer are also performed in accordance withthis method.

Methods of making hot swappable network servers are also provided. Forexample, one embodiment comprises a method of electrically coupling acentral processing unit of a network server to a plurality of networkinterface modules comprising the acts of routing an I/O bus having afirst format from the central processing unit to primary sides of aplurality of bus adaptor chips and routing an I/O bus of the same firstformat from a secondary side of the bus adaptor chips to respective onesof the network interface modules.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows one embodiment of a network server in accordance with theinvention including a fault tolerant computer system mounted on a rack.

FIG. 2 is a block diagram illustrating certain components and subsystemsof the fault tolerant computer system shown in FIG. 1.

FIG. 3A shows the chassis with network interface modules and powermodules.

FIG. 3B is an exploded view which shows the chassis and theinterconnection assembly module.

FIG. 3C is an illustration of the interconnection assembly module ofFIG. 3B.

FIG. 4 shows a front view of an embodiment of a network server in achassis mounted on a rack.

FIG. 5A is a view showing the front of the backplane printed circuitboard of an interconnection assembly module in the network server.

FIG. 5B is a view showing the back of the backplane printed circuitboard of the interconnection assembly module in the network server.

FIG. 6 is an exploded view which shows the elements of one embodiment ofa network interface module of the network server.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will now be described withreference to the accompanying Figures, wherein like numerals refer tolike elements throughout. The terminology used in the descriptionpresented herein is intended to be interpreted in its broadestreasonable manner, even though it is being utilized in conjunction witha detailed description of certain specific embodiments of the presentinvention. This is further emphasized below with respect to someparticular terms used herein. Any terminology intended to be interpretedby the reader in any restricted manner will be overtly and specificallydefined as such in this specification.

FIG. 1 shows one embodiment of a network server 100. It will beappreciated that a network server 100 which incorporates the presentinvention may take many alternative configurations, and may include manyoptional components currently used by those in the art. A specificexample of one such configuration is described in conjunction with FIG.1. The operation of those portions of the server 100 which areconventional are not described in detail.

In the server of FIG. 1, a cabinet 101 houses a rack 102, on which ismounted several data processing, storage, and display components. Theserver 100 may include, for example, a display monitor 173A resting on amonitor shelf 173B mounted on the rack 102 as well as a retractablekeyboard 174. Also included are a variable number of data storagedevices 106, which may be removably mounted onto shelves 172 of the rack102. One embodiment as shown in FIG. 1 has twenty data storage modules106 removably mounted individually on four shelves 172 of the rack 102,with five data storage modules 106 per shelf. A data storage module maycomprise magnetic, optical, or any other type of data storage media. Inthe embodiment illustrated in FIG. 1, one data storage module is aCD-ROM module 108.

In advantageous embodiments described in detail with reference to FIGS.2-6 below, the network server includes a fault tolerant computer systemwhich is mounted in a chassis 170 on the rack 102. To provide previouslyunavailable ease in maintenance and reliability, the computer system maybe constructed in a modular fashion, including a CPU module 103, aplurality of network interface modules 104, and a plurality of powermodules 105. Faults in individual modules may be isolated and repairedwithout disrupting the operation of the remainder of the server 100.

Referring now to FIG. 2, a block diagram illustrating several componentsand subsystems of the fault tolerant computer system is provided. Thefault tolerant computer system may comprise a system board 182, abackplane board 184 which is interconnected with the system board 182,and a plurality of canisters 258, 260, 262, and 264 which interconnectwith the backplane board 184. A number ‘n’ of central processing units(CPUs) 200 are connected through a host bus 202 to a memory controller204, which allows for access to semiconductor memory by the other systemcomponents. In one presently preferred embodiment, there are four CPUs200, each being an Intel Pentium Pro microprocessor. A number of bridges206, 208 and 210 connect the host bus to three additional bus systems212, 214, and 216. The bus systems 212, 214 and 216, referred to as PCbuses, may be any standards-based bus system such as PCI, ISA, EISA andMicrochannel. In one embodiment of the invention, the bus systems 212,214, 216 are PCI. In another embodiment of the invention a proprietarybus is used.

An ISA Bridge 218 is connected to the bus system 212 to support legacydevices such as a keyboard, one or more floppy disk drives and a mouse.A network of microcontrollers 225 is also interfaced to the ISA bus 226to monitor and diagnose the environmental health of the fault tolerantsystem.

The two PC buses 214 and 216 contain bridges 242, 244, 246 and 248 to PCbus systems 250, 252, 254, and 256. As with the PC buses 214 and 216,the PC buses 250, 252, 254 and 256 can be designed according to any typeof bus architecture including PCI, ISA, EISA, and Microchannel. The PCbuses 250, 252, 254 and 256 are connected, respectively, to a canister258, 260, 262 and 264. These canisters are casings for a detachable bussystem and provide multiple slots for adapters. In the illustratedcanister, there are four adapter slots. The mechanical design of thecanisters is described in more detail below in conjunction with FIG. 6.

The physical arrangement of the components of the fault tolerantcomputer shown in FIG. 2 are illustrated further in FIGS. 3A, 3B, and3C. Referring now to FIG. 3A, a chassis 170 is mounted on chassismounting rails 171 so as to be secured to the rack 102 of FIG. 1. Thechassis includes a front 170A, back 170B, sides 170C and 170D, as wellas a top 170E and a bottom 170F. Although not shown in FIG. 3A, sets ofperforations 177 in such patterns and numbers to provide effectivecooling of the internal components of the chassis 170 are also providedin its housing panels.

A central processing unit (CPU) module 103 which may advantageouslyinclude the system board 182 of FIG. 2 is removably mounted on achassis. A plurality of network interface modules 104 are also removablymounted on the chassis 170. The network interface modules 104 maycomprise the multiple-slot canisters 258, 260, 262, and 264 of FIG. 2.Two redundant power modules 105 are additionally removably mounted onthe chassis 170. The CPU module 103, the network interface modules 104,and the power modules 105, when removably mounted may have their frontspositioned in the same plane as the chassis front 170A.

In this embodiment, the CPU module 103 is removably mounted on the topchassis shelf 175A. The next chassis shelf 175B below holds tworemovably mounted network interface modules 104 and one removablymounted power module 105. The remaining chassis shelf 175C also holdstwo removably mounted network interface modules 104 and one removablymounted power module 105. The network interface modules 104 and thepower modules 105 are guided into place with the assistance of guiderails such as guide rail 180.

In one embodiment of the invention, the network interface modules 104and the power modules 105 are connected to the CPU module 103 through aninterconnection assembly module 209 (illustrated in additional detail inFIGS. 3B and 3C) which advantageously includes the backplane board 184illustrated in FIG. 2. The interconnection assembly module electricallyterminates and isolates the rest of the network server 100 from the PCBus local to any given network interface module 104 when that networkinterface module 104 is removed and replaced without powering down thenetwork server 100 or the CPU module 103. The physical layout of oneembodiment of the interconnection assembly module is described in moredetail below with reference to FIGS. 5A and 5B.

FIG. 3B illustrates the chassis 170 for the fault tolerant computersystem 170 in exploded view. With the interconnection assembly module209 installed in the rear, interconnection assembly module 209 mayprovide a communication path between the CPU module 103 and the networkinterface modules 104. In this embodiment, the interconnection assemblymodule 209 is mounted on the chassis back 170B such that it is directlybehind and mates with the chassis modules 103, 104 and 105 when they aremounted on the chassis 170.

Thus, with the interconnection assembly module 209 mounted on thechassis 170, the network interface modules 104 can be brought in and outof connection with the network server 100 by engaging and disengagingthe network interface module 104 to and from its associated backplaneboard connector. One embodiment of these connectors is described inadditional detail with reference to FIG. 3C below. This task may beperformed without having to power down the entire network server 100 orthe CPU module 103. The network interface modules 104 are thus hotswappable in that they may be removed and replaced without powering downthe entire network server 100 or the CPU module 103.

In FIG. 3C, a specific connector configuration for the interconnectionassembly module 209 is illustrated. As is shown in that Figure, fourconnectors 413, 415, 417, and 419 are provided for coupling torespective connectors of the network interface modules 104. Twoconnectors 421 are provided for the power modules 105. Another connector411 is configured to couple with the CPU module 103. The process ofinterconnecting the network interface modules 104 and the CPU module 103to the interconnection assembly module 209 is facilitated by guidingpegs 412, 414, 416, 418, 420 on the connectors of the interconnectionassembly module 209 which fit in corresponding guiding holes in thenetwork interface modules 104 and CPU module 103. The interconnectionassembly module 209 also includes two sets of perforations 422sufficient in number and in such patterns so as to assist with thecooling of each power module 105. This embodiment has two sets ofperforations 422 adjacent each power module connector 421.

FIG. 4 is a front view of the network server cabinet 101 housing apartially assembled fault tolerant computer system mounted on a rack102. In this Figure, the interconnection assembly module 209 is visiblethrough unoccupied module receiving spaces 201, 203, and 205. The CPUmodule 103 has not yet been mounted on the chassis as evidenced by theempty CPU module space 203. As is also illustrated in FIG. 1, severalnetwork interface modules 104 are present. However, one of the networkinterface modules remains uninstalled as evidenced by the empty networkinterface module space 201. Similarly, one power module 105 is present,but the other power module has yet to be installed on the chassis 170 asevidenced by the empty power module space 205.

In this Figure, the front of the interconnection assembly module 209mounted on the rear of the chassis is partially in view. FIG. 4 thusillustrates in a front view several of the connectors on the backplaneboard 184 used for connecting with the various chassis modules when thechassis modules are removably mounted on the chassis 170. As alsodescribed above, the CPU module 103 may be removably mounted on the topshelf 175A of the chassis in the empty CPU module space 203. As brieflyexplained above with reference to FIGS. 3A through 3C, the CPU module103 has a high density connector which is connected to the high densityconnector 411 on the back of the backplane printed circuit board 184when the CPU module is mounted on the top shelf 175A of the chassis 170.The chassis 170 and the guiding peg 412 assist in creating a successfulconnection between the 360 pin female connector 411 and the 360 maleconnector of the CPU module 103. The guiding peg 412 protrudes from thebackplane printed circuit board front and slip into correspondingguiding holes in the CPU module 103 when the CPU module 103 is mountedon the shelf 175A of the chassis 170.

In addition, one of the high density connectors 413 which interconnectsthe backplane printed circuit board 184 with one of the networkinterface modules 104 is shown in FIG. 4. In the illustratedembodiments, there are four high density connectors, one connecting toeach network interface module 104. The high density connector 413 may bea 180 pin female connector. This 180 pin female connector 413 connectsto a 180 pin male connector of the network interface module 104 when thenetwork interface module 104 is removably mounted on the middle shelf175B of the chassis in the empty network interface module space 201. Thechassis, the two guiding pegs (of which only guiding peg 414 is shown inFIG. 4), and the chassis guide rail 180 assist in creating a successfulconnection between the 180 pin female connector 413 and the 180 pin maleconnector of the network interface module 104. The two guiding pegs, ofwhich only guiding peg 414 is within view, protrude from the front ofthe backplane printed circuit board and slip into corresponding guidingholes in the network interface module 104 when the network interfacemodule 104 is removably mounted on a shelf of the chassis.

FIG. 5A is a view showing the front side of the backplane printedcircuit board 184. In this embodiment, the backplane printed circuitboard 184 is configured to be mounted on the chassis rear directlybehind the chassis modules comprising the CPU module 103, the networkinterface modules 104, and the power modules 105. The backplane printedcircuit board 184 may be rectangularly shaped with two rectangularnotches 423 and 424 at the top left and right.

As is also shown in FIG. 3C, the backplane printed circuit board 184also has high density connectors 413, 415, 417 and 419 which connect tocorresponding network interface modules 104. Each high density connectorhas a pair of guiding pegs 414, 416, 418, and 420 which fit intocorresponding guiding holes in each network interface module 104. Thebackplane printed circuit board also mounts a high density connector 411and a guiding peg 412 for connecting with the CPU module 103 and twoconnectors 421 for connecting with the power modules 105. The backplaneprinted circuit board 184 may also include sets of perforations 422sufficient in number and in such patterns so as to assist with thecooling of each power module 105. The perforations 422 are positioned inthe backplane printed circuit board 184 directly behind the powermodules 105 when the power modules 105 are removably mounted on theshelves 175B and 175C of the chassis.

FIG. 5B shows the rear side of the backplane printed circuit board 184.The back of the connectors 421 that connect to the connectors of thepower modules 105 are illustrated. Also, the rear of the high densityconnectors 413, 415, 417 and 419 which connect to the network interfacemodules 104 are also present on the backplane printed circuit board backto connect to the backplane printed circuitry. As shown in this Figure,each high density connector 413, 415, 417, 419 is attached to aninput/output (I/O) bus 341, 344, 349 or 350. In one advantageousembodiment, the I/O bus is a peripheral component interconnect (PCI)bus.

In one embodiment of the present invention, the I/O buses 341, 344, 349,and 350 are isolated by bus adapter chips 331, 332, 333 and 334. Thesebus adapter chips 331, 332, 333, and 334 provide, among other services,arbitered access and speed matching along the I/O bus. One possibleembodiment uses the DEC 21152 Bridge chip as the bus adapter 331, 332,333 or 334.

Several advantages of the present invention are provided by the busadapter chips 331 through 334 as they may be configured to provideelectrical termination and isolation when the corresponding networkinterface module 104 has been removed from its shelf on the chassis.Thus, in this embodiment, the bridge 331, 332, 333 or 334 acts as aterminator so that the removal and replacement of a network interfacemodule 104 from its shelf of the chassis 170, through an electricalremoval and insertion is not an electrical disruption on the primaryside of the bridge chip 331, 332, 333 or 334. It is the primary side ofthe bridge chip 331B, 332B, 333B or 334B which ultimately leads to theCPU module 103. Thus, the bridge chip 331, 332, 333 or 334 providesisolation for upstream electrical circuitry on the backplane printedcircuit board 184 and ultimately for the CPU module 103 through anarbitration and I/O controller chip 351 or 352. As mentioned above, thisembodiment uses a PCI bus for the I/O bus. In such an instance, thebridge chip is a PCI to PCI bridge. The arbitration and I/O controllerchip 351 or 352 (not illustrated in FIG. 2 above) determines arbiteredaccess of the I/O bus and I/O interrupt routing. The I/O bus 343 or 346then continues from the arbitration and I/O controller chip 351 or 352to the back side of the high density connector 411 that connects withthe corresponding high density connector of the CPU module 103 when theCPU module 103 is mounted on the top shelf 175A of the chassis 170.

FIG. 6 shows aspects of one embodiment of a network interface module104. The modularity provided by the canister configuration provides easeof maintenance. Referring now to this Figure, the network interfacemodule 104 comprises a canister 560 with a front 560A, back 560B, sides560C, top 560D and bottom 560E. The canister front 560A may bepositioned proximate the front of the chassis when the canister isremovably mounted on a shelf of the chassis. A printed circuit board 561is secured flat against the canister side 560C inside the canister 560.The printed circuit board 561 comprises an I/O bus. As described above,in one advantageous embodiment, the I/O bus is a PCI bus. A plurality ofinterface card slots 562, are attached to the I/O bus. The number ofallowed interface card slots is determined by the maximum load the I/Obus can handle. In the illustrated embodiment, four interface card slots562 are provided, although more or less could alternatively be used.Also connected to the I/O bus and on one end of the printed circuitboard 561 is a high density connector 563 which mates with one of thehigh density connectors on the backplane board 184. Above and below theconnector 563 is a solid molding with a guiding hole. These two guidingholes correspond with a pair of guiding pegs 414, 416, 418, or 420 whichalong with the chassis and the chassis guiding rails assist, when thecanister 560 is removably mounted, in bringing together or mating the180 pin male connector 563 at one end of the printed circuit board 561and the 180 pin female connector 413, 415, 417 or 419 on the backplaneprinted circuit board 184.

Interface cards may be slipped into or removed from the interface cardslots 562 when the canister 560 is removed from its shelf 175B or 175Cin the chassis 170. An interface card slot 562 be empty or may be filledwith a general interface card. The general interface card may be anetwork interface card (NIC) such as, but not limited to, an Ethernetcard or other local area network (LAN) card, with a corresponding NICcable connected to the NIC and routed from the server 100 to a LAN. Thegeneral interface card may be a small computer system interface (SCSI)controller card with a corresponding SCSI controller card cableconnected to the SCSI controller card. In this embodiment, the SCSIcontroller card is connected by a corresponding SCSI controller cardcable to a data storage module which may be connected to data storagemodules such as hard disks 106 or other data storage device.Furthermore, the general interface card need not be a NIC or an SCSIcontroller card, but may be some other compatible controller card. Thecanister front 560A also has bay windows 564 from which the generalinterface card cable may attach to a general interface card. Unused baywindows may be closed off with bay window covers 565.

The network interface module 104 also has a novel cooling system. Eachnetwork interface module 104 extends beyond the chassis rear, and inthis portion, may include a pair of separately removable fans 566A and566B. The separately removable fans are positioned in series with oneseparately removable fan 566B behind the other separately removable fan566A. The pair of separately removable fans 566A and 566B run at reducedpower and reduced speed unless one of the separately removable fans 566Aor 566B fails, in which case, the remaining working separately removablefan 566B or 566A will run at increased power and increased speed tocompensate for the failed separately removable fan 566A or 566B. Theplacement of the separately removable fans 566A and 566B beyond thechassis rear make them readily accessible from the behind the rack 102.Accessibility is desirable since the separately removable fans 566A and566B may be removed and replaced without powering down or removing thenetwork interface module 104.

To further assist with the cooling of the canister 560, the canister 560has sufficient sets of perforations 567 in such pattern to assist incooling the canister 560. In this embodiment, the perforations 567 areholes in the canister 560 placed in the pattern of roughly a rectangularregion.

A significant advantage of this embodiment is the ability to change ageneral interface card in a network server 100 without powering down thenetwork server 100 or the CPU module 103. To change a general interfacecard, it is desirable to first identify the bridge chip 331, 332, 333 or334 whose secondary side is connected to the network interface module104 containing the general interface card to be changed.

Assuming that the general interface card that needs to be changed is inthe network interface module 104 which is connected by PCI bus and highdensity connector to bridge chip 331, to remove the network interfacemodule 104 without disrupting operation of the other portions of theserver 100, the bridge chip 331 may become an electrical termination toisolate the electrical hardware of the network server from theelectrical removal or insertion on the bridge chip secondary side 331A.This may be accomplished by having the CPU module 103 place thesecondary side 331A, 332A, 333A or 334A of the bridge into a reset modeand having circuitry on the printed circuit board 561 of the networkinterface module 104 power down the canister 560 including the generalinterface cards within the canister 560. Once the canister 560 ispowered down and the bridge chip has electrically isolated the networkinterface module from the rest of the electrical hardware in the networkserver 100, then the network interface module 104 may be pulled out itsshelf 175B in the chassis 170. After the network interface module 104has been removed, then the general interface card can be removed fromits interface card slot 562 and replaced. Subsequently, the networkinterface module 104 is removably mounted again on the shelf 175B in thechassis 170. The electrical hardware on the printed circuit board 561 ofthe network interface module 104 may then power up the canister 560including the general interface cards within the canister 560. Thebridge chip secondary side 331A, 332A, 333A or 334A is brought out ofreset by the CPU module 103 and the network interface module 104 isagain functional.

At no time during the procedure did the network server 100 or the CPUmodule 103 have to be powered down. Although the one network interfacemodule 104 was powered down during the procedure, the other networkinterface modules were still functioning normally. In fact, anyworkstation connected to the network server 100 by means other than theaffected network interface module 104 would still have total access tothe CPU module 103, the other network interface modules, and all thenetworks and data storage modules such as, but not limited to harddisks, CD-ROM modules, or other data storage devices that do not relyupon the general interface cards inside the removed network interfacemodule. This is a desired advantage since network server down time canbe very costly to customers and to vendors, can create poor customeropinion of the vendor, vendors products and services, and decreaseoverall computing throughput.

The foregoing description details certain embodiments of the presentinvention and describes the best mode contemplated. It will beappreciated, however, that no matter how detailed the foregoing appearsin text, the invention can be practiced in many ways. As is also statedabove, it should be noted that the use of particular terminology whendescribing certain features or aspects of the present invention shouldnot be taken to imply that the broadest reasonable meaning of suchterminology is not intended, or that the terminology is being re-definedherein to be restricted to including any specific characteristics of thefeatures or aspects of the invention with which that terminology isassociated. The scope of the present invention should therefore beconstrued in accordance with the appended claims and any equivalentsthereof.

Appendix A Incorporation by Reference of Commonly Owned Applications

The following patent applications, commonly owned and filed on the sameday as the present application are hereby incorporated herein in theirentirety by reference thereto:

Appli- cation Attorney Title No. Docket No. “System Architecture forRemote MNFRAME.002A1 Access and Control of Environmental Management”“Method of Remote Access and Control MNFRAME.002A2 of EnvironmentalManagement” “System for Independent Powering of MNFRAME.002A3 DiagnosticProcesses on a Computer System” “Method of Independent Powering ofMNFRAME.002A4 Diagnostic Processes on a Computer System” “Diagnostic andManaging Distributed MNFRAME.005A1 Processor System” “Method forManaging a Distributed MNFRAME.005A2 Processor System” “System forMapping Environmental MNFRAME.005A3 Resources to Memory for ProgramAccess” “Method for Mapping Environmental MNFRAME.005A4 Resources toMemory for Program Access” “Hot Add of Devices Software MNFRAME.006A1Architecture” “Method for The Hot Add of Devices” MNFRAME.006A2 “HotSwap of Devices Software MNFRAME.006A3 Architecture” “Method for The HotSwap of Devices” MNFRAME.006A4 “Method for the Hot Add of a NetworkMNFRAME.006A5 Adapter on a System Including a Dynamically Loaded AdapterDriver” “Method for the Hot Add of a Mass MNFRAME.006A6 Storage Adapteron a System Including a Statically Loaded Adapter Driver” “Method forthe Hot Add of a Network MNFRAME.006A7 Adapter on a System Including aStatically Loaded Adapter Driver” “Method for the Hot Add of a MassMNFRAME.006A8 Storage Adapter on a System Including a Dynamically LoadedAdapter Driver” “Method for the Hot Swap of a Network MNFRAME.006A9Adapter on a System Including a Dynamically Loaded Adapter Driver”“Method for the Hot Swap of a Mass MNFRAME.006A10 Storage Adapter on aSystem Including a Statically Loaded Adapter Driver” “Method for the HotSwap of a Network MNFRAME.006A11 Adapter on a System Including aStatically Loaded Adapter Driver” “Method for the Hot Swap of a MassMNFRAME.006A12 Storage Adapter on a System Including a DynamicallyLoaded Adapter Driver” “Method of Performing an Extensive MNFRAME.008ADiagnostic Test in Conjunction with a BIOS Test Routine” “Apparatus forPerforming an Extensive MNFRAME.009A Diagnostic Test in Conjunction witha BIOS Test Routine” “Configuration Management Method for MNFRAME.010AHot Adding and Hot Replacing Devices” “Configuration Management Systemfor MNFRAME.011A Hot Adding and Hot Replacing Devices” “Apparatus forInterfacing Buses” MNFRAME.012A “Method for Interfacing Buses”MNFRAME.013A “Computer Fan Speed Control Device” MNFRAME.016A “ComputerFan Speed Control Method” MNFRAME.017A “System for Powering Up andPowering MNFRAME.018A Down a Server” “Method of Powering Up and PoweringMNFRAME.019A Down a Server” “System for Resetting a Server” MNFRAME.020A“Method of Resetting a Server” MNFRAME.021A “System for DisplayingFlight MNFRAME.022A Recorder” “Method of Displaying Flight MNFRAME.023ARecorder” “Synchronous Communication MNFRAME.024A Interface”“Synchronous Communication MNFRAME.025A Emulation” “Software SystemFacilitating the MNFRAME.026A Replacement or Insertion of Devices in aComputer System” “Method for Facilitating the MNFRAME.027A Replacementor Insertion of Devices in a Computer System” “System ManagementGraphical User MNFRAME.028A Interface” “Display of System Information”MNFRAME.029A “Data Management System Supporting MNFRAME.030A Hot PlugOperations on a Computer” “Data Management Method SupportingMNFRAME.031A Hot Plug Operations on a Computer” “Alert Configurator andManager” MNFRAME.032A “Managing Computer System Alerts” MNFRAME.033A“Computer Fan Speed Control System” MNFRAME.034A “Computer Fan SpeedControl System MNFRAME.035A Method” “Black Box Recorder for InformationMNFRAME.036A System Events” “Method of Recording InformationMNFRAME.037A System Events” “Method for Automatically Reporting aMNFRAME.040A System Failure in a Server” “System for AutomaticallyReporting a MNFRAME.041A System Failure in a Server” “Expansion of PCIBus Loading MNFRAME.042A Capacity” “Method for Expanding PCI BusMNFRAME.043A Loading Capacity” “System for Displaying System Status”MNFRAME.044A “Method of Displaying System Status” MNFRAME.045A “A Methodfor Communicating a MNFRAME.048A Software Generated Pulse WaveformBetween Two Servers in a Network” “A System for Communicating aMNFRAME.049A Software Generated Pulse Waveform Between Two Servers in aNetwork” “Method for Clustering Software MNFRAME.050A Applications”“System for Clustering Software MNFRAME.051A Applications” “Method forAutomatically Configuring MNFRAME.052A a Server after Hot Add of aDevice” “System for Automatically Configuring MNFRAME.053A a Serverafter Hot Add of a Device” “Method of Automatically ConfiguringMNFRAME.054A and Formatting a Computer System and Installing Software”“System for Automatically Configuring MNFRAME.055A and Formatting aComputer System and Installing Software” “Determining Slot Numbers in aMNFRAME.056A Computer” “System for Detecting Errors in a MNFRAME.058ANetwork” “Method of Detecting Errors in a MNFRAME.059A Network” “Systemfor Detecting Network Errors” MNFRAME.060A “Method of Detecting NetworkErrors” MNFRAME.061A

What is claimed is:
 1. A method of electrically coupling a centralprocessing unit (CPU) of a network server to a plurality of interfacemodules comprising: routing an I/O bus having a first format from saidcentral processing unit to primary sides of a plurality of bus adapterchips; routing an I/O bus of said first format from secondary sides ofsaid bus adapter chips to respective ones of said interface modules,wherein the bus adapter chips comprise electrical hardware whichprovides arbitered access along the I/O buses and wherein the steps ofrouting the I/O buses to and from bus adapter chips compriseselectrically isolating the CPU from electrical disruption when one ofthe interface modules is removed.
 2. The method of claim 1, wherein eachof said plurality of interface modules is a network interface module. 3.The method of claim 1, further including mounting a plurality ofinterface cards in interface card slots in said plurality of interfacemodules.
 4. The method of claim 1, further including removably mountingsaid interface modules on a chassis.
 5. The method of claim 4, whereinthe act of removably mounting the interface module comprises the act ofmounting said interface module such that said interface module may beremoved from said chassis and disconnected electrically from said CPU ormounted on said chassis and connected electrically to said CPU withoutpowering down said CPU.
 6. A method of electrically coupling a pluralityof interface modules to a CPU such that at least one of the interfacemodules can be disconnected without powering down the remaininginterface modules or the CPU, said method comprising: mounting a CPU ona chassis; removably mounting a plurality of interface modules to saidchassis; mounting a backplane printed circuit board on the chassis,wherein the backplane printed circuit board comprises at least one busadapter chip for each of the plurality of interface modules, and whereineach bus adapter chip has a primary side and a secondary side, andwherein each bus adapter chip has electrical hardware that isolates theprimary side from the secondary side when the corresponding interfacemodule has been removed from the chassis; routing an I/O bus on saidbackplane printed circuit board from the primary side of the at leastone bus adapter chip to the CPU; and routing an I/O bus on saidbackplane printed circuit board from the secondary side of the at leastone bus adapter chip to the corresponding one of the interface modules,wherein the at least one bus adapter chip comprises electrical hardwareproviding arbitered access and speed matching along the I/O busses. 7.The method of claim 6, wherein each of said plurality of interfacemodules is a network interface module.
 8. The method of claim 6, whereinthe I/O busses comprise peripheral component interconnect (PCI) busses.9. The method of claim 8, wherein said act of mounting the plurality ofinterface modules to the backplane printed circuit board comprises theacts of: connecting a 180 pin female connector on said backplane printedcircuit board with a 180 pin male connector on a interface module ofsaid plurality of interface modules; and connecting a 360 pin femaleconnector on said backplane printed circuit board with a 360 pin maleconnector on said CPU.
 10. The method of claim 6, further includingmounting a plurality of interface cards in interface card slots in saidplurality of interface modules.
 11. The method of claim 10, wherein saidprinted circuit board powers down said interface modules including saidinterface cards thereon.
 12. A method of electrically coupling aplurality of interface modules to a CPU such that at least one of theinterface modules can be removed without powering down the remaininginterface modules or the CPU, said method comprising: mounting abackplane printed circuit board on the back of a chassis; connecting aCPU module to said backplane printed circuit board when mounting a CPUmodule on said chassis; and removably mounting a plurality of interfacemodules to the backplane printed circuit board; and connecting theplurality of interface modules to the backplane printed circuit boardwith bus adapter chips configured to provide arbitrated access to saidinterface modules and electrical termination and isolation between theinterface modules and the CPU module when a interface module is removed.13. The method of claim 12, wherein each of said plurality of interfacemodules is a network interface module.
 14. The method of claim 12, wheresaid act of connecting said interface module to said backplane printedcircuit board comprises the act of connecting a high density connectorof said interface module to a high density connector on said backplaneprinted circuit board.
 15. The method of claim 14, further includingmounting a plurality of interface cards in interface card slots in saidplurality of interface modules.